The present invention pertains generally to a system for applying current flow to the brakes of a towed vehicle during braking of a tow vehicle.
Common in the recreational trailer field is the use of electric brakes actuated during braking of a tow vehicle by various types of electric and electronic brake controllers located in the tow vehicle.
In spite of substantial effort to provide braking systems for such towed vehicles, a problem remains in satisfactory regulating the electrically actuated brakes of such towed vehicles. Periodic adjustment of trailer braking systems by skilled personnel is necessary to provide adequate braking operation. As trailer brakes are, for the most part, electric the control of current flow to such brakes must be in fine increments.
Efforts in the past have included inertia responsive pendulums in brake controllers located within the tow vehicle which controllers are separate from the tow vehicle hydraulic brake system. An example of such an inertia responsive controller is disclosed in U.S. Pat. No. 3,909,075. For one reason or another such inertial responsive controllers do not overcome the above objections to known braking systems. Such controllers function only when a pendulum responds to changes in speed of the tow vehicle. A number of U.S. patents disclose the combination of a brake controller which, at least partially, relies on a piston actuated by the tow vehicle hydraulic brake system to displace an electrical contact for engagement with a resistor at points along the latter with current flow from the resistor to electrical trailer brakes being determined by the point along the resistor at which contact is made by the hydraulically biased contact member. Examples of the immediately above described controllers are found in U.S. Pat. Nos. 3,704,042, 3,524,159, 3,740,691, 3,328,739 and 4,233,587. All such known braking systems dependent upon hydraulic pressure from the tow vehicle's braking system encounter the drawback of tapping into the master cylinder output line. Further, on vehicles equipped with an antilock brake system such tapping into a master cylinder output line would jeopardize system operation. The prior art systems utilizing hydraulically actuated plungers, pistons, etc., to position a contact into engagement with the coil of a resistor incurs fluid displacement and possible loss by wear of mechanical components. Current brake controllers for regulating current flow to the electric brakes of trailers rely solely on mechanical and electric components to regulate current flow to the brakes.